Temperature dependence of Bi behavior in MBE growth of InGaAs/InP

The behavior of bismuth (Bi) in the molecular beam epitaxy (MBE) growth of InGaAs/InP was investigated in situ by reflection high energy electron diffraction (RHEED) and ex situ by X-ray diffraction (XRD) and atomic force microscopy (AFM). It was found that the behavior of Bi in InGaAs growth can be divided into two categories: incorporation and surfactant, depending on the growth temperature. A low growth temperature was favored for Bi incorporation in InGaAs to form the quaternary InGaAsBi alloy. The amount of incorporated Bi rapidly decreased with increasing growth temperature. At the normal MBE growth temperature for InGaAs/InP, 450 °C, no Bi is incorporated in InGaAs films. However, Bi can act as a surfactant during the MBE growth of InGaAs/InP at that temperature because it changes the growth mode from 3D to 2D as growth begins, and it improves surface smoothness, as confirmed by RHEED and AFM results.